1. Field of the Invention
The present invention relates to a digital television receiver (TV), and more particularly, to an apparatus and method for converting formats of input video signals of diverse types into formats of output video signals of diverse types through a single integrated block.
2. Discussion of the Related Art
Generally, there are a great variety of standard for a video signal and a display for displaying the same. Namely, there are standard of the video signal such as a conventional analog TV signal (for example, NTSC/PAL/SECAM), a VCR signal, a computer PC signal (for example, VGA to UXGA) as well as a recent digital TV signal (for example, ATSC/DVB/ARIB) according to a system to be applied.
Moreover, there are various displays for displaying the video signal such as a conventional cathode ray tube (CRT) and a projection, which are widely used as well as a plasma display panel, and a liquid crystal display, which are developed in recent, and a computer etc.
More especially, the development and popularization of the digital TV gradually increase the need to correspond to the various video standard and displays, and the semiconductor process technology has been developed so that various functions show a tendency to be integrated into one chip.
Contrary to the analog TV, the digital TV supports a multi-format. For example, the ATSC standard of the United States digital TV broadcasting standard defines 18 broadcasting formats. Here, the format means following four, namely a space resolution, a frame rate, scanning method, and an aspect ratio.
1. Space resolution: 720×480, 1280×720, 1920×1080, etc.
2. Frame rate: 24, 30, 59.94, 60, 80 Hz, etc.
3. Scan: Interlaced scan, Progressive scan
4. Aspect ratio: 4:3, 16:9, 14:9, etc.
Namely, the digital TV can receive videos having various sizes such as a high definition (HD) video, a standard definition (SD) video, a computer video signal, and an analog signal, so that can process the various videos. As described above, a various output format is required according to the various type displays.
Accordingly, there is a demand for an apparatus for converting respective input format into desired output format.
According to the conventional art, a format conversion is defined for the space resolution, the frame rate, and the scan method. A recent method is proposed to adding the aspect ratio.
Therefore, a format converting apparatus of the digital TV converts inputted signal with various formats, for example, the space resolution of the inputted video, the frame rate, the scanning method, and the aspect ratio into desired output formats.
FIG. 1 illustrates a block diagram of a format converting apparatus of a conventional digital TV.
Namely, it is assumed that an RF type DTV signal is modulated in a way of vestigial sideband (VSB). An VSB demodulating unit 101 demodulates the RF type DTV signal and outputs the demodulated signal to a transport (TS) demultiplexer 102 in a transport stream type. The TS demultiplexer 102 selects a desired single program from a plurality of programs contained in one channel, separates an audio and video bitstreams multiplexed in the selected program, and outputs the separated video bitstream to a video decoder 103 and separated audio bitstream to an audio decoder 105.
The video decoder 103 eliminates an overhead (various header information, a start code, etc.) from the input video bitstream, makes a pure data information undergo a variable length decoding (VLD), and restores the pure data information into an original screen's pixel value through an inverse quantizing procedure, an inverse discrete cosine transform (IDCT) procedure, and a motion compensating procedure using a motion vector, so that outputs the deocoded picture to a format converting unit 104. The audio decoder 105 decodes the audio bitstream encoded by using an MPEG algorithm or an Dolby (AC)-3 algorithm and outputs the decoded audio PCM data through a speaker.
The format converting unit 104 extracts four format information, that is, the resolution, the frame rate, the scan method, and the aspect ratio contained in the digital broadcasting signal transmitted from a broadcasting station, and performs the conversion of the input video to the output video format (for example, 1920×1080 30i 16:9, i indicates the interlaced scan) suitable to the display by using the extracted format information.
However, the format converting apparatus for a DTV illustrated in FIG. 1 can perform the format conversion for the digital broadcasting signal, but had problems to support the format conversion of other video signals (for example, an analog TV signal, a computer video signal, and a component signal, etc.).
In other words, since there is prepared the format converting unit for processing the digital TV signal but a format converting unit for processing other video signal, there is a need for further format converting unit as illustrated in FIG. 2.
FIG. 2 illustrates a block diagram showing an example of a format converting apparatus for converting format the other video signal except for the conventional digital TV signal, and has a disadvantage that a format converting unit 205 for format-converting the analog TV signal, the computer video signal, and the component signal should be added in the apparatus illustrated in FIG. 1. At that time, the format-converted video signal by a DTV format converting unit 204 or the added format converting unit 205 is selectively outputted through a multiplexer 206.
At that time, the analog TV signal, the component signal, and the computer video signal1 are produced according to the standards such as CCIR Recommendations 601 format (D1), EIA770.1˜EIA770.3, and VESA, and do not contain the format information. Therefore, the format converting unit 205 performs the format-conversion by detecting the format of video from the inputted signals or being noticed by a user.
Consequently, the added format converting unit 205 illustrated in FIG. 2, has a construction as illustrated in FIG. 3 for overcoming the disadvantages as described above.
FIG. 3 illustrates a detail block diagram of the format converting unit in FIG. 2.
For example, if an NTSC composite video signal is inputted, an NTSC decoder 301 separates a horizontal/vertical synchronized signal, a brightness signal Y, and a color signal C. If necessary, a color converting unit 302 performs a color space conversion (for example, YIQ→YCbCr) and inputs the converted signals into a format converting unit 306. The format converting unit 306 should support the chroma format 4:4:4 or 4:2:2 in addition to 4:2:0 (digital broadcasting video).
Moreover, the computer video signal, VGA˜UXGA, etc., is inputted through an RGB input unit 303 in the form of an RGB, and if necessary, is inputted into the format converting unit 306 after the color space conversion (for example, RGB→YCbCr) are performed. The component signal, 480i through 1080i is directly inputted into the format converting unit 306 through the input unit 305.
As described above, according to the conventional art, in order to process an additional video signal such as the analog TV signal, the computer video signal, and the component signal, the respective color space conversion should be independently performed and the format converting unit should support the chroma format conversion as illustrated in FIG, 3.
This system has a disadvantage that a corresponding block should be continuously added from exterior of the format converting unit 204 of the digital TV whenever the video input signal is added.
Moreover, in order to connect the format-converted signal with the various displays, a gamma correction, and a geometric correction should be performed by considering a specific characteristic of the display, but there is occurred a problem to add the above added circuit whenever the display is changed. Here, the gamma correction means the correction for various distortions2 occurring from the color characteristic of the display. The gamma correction is applied to all display. Moreover, the geometric correction means the correction for various geometric distortion3 occurring from the display characteristic as illustrated in FIGS. 4A through 4D. More particularly, in the CRT and the projection type, the problem is very serious, but in the PDP and LCD, the same problem does not occur.
As described above, the conventional format-conversion method has a disadvantage that new hardware should be added into the format converting unit so as for the corresponding conversion whenever an external video signal is added. When the tendency for integrating a plurality of media into the digital TV in the future more and more, it can be forecasted for more various video signals to be inputted so that the external converting unit is gradually increased and the hardware can be bigger and bigger.